Pump



May 2, 1961 M. W. HUBER l2,982,216

PUMP

Filed Dec. 14, 195e ATTORNEYS v BY Y PUMP Matthew W. Huber, Watertown,N.Y., assignor to The New York Air Brake Company, a corporation of NewJersey l Filed Dec. 14,1956, ser. No. 628,366

a claims. (cl. s-37) This invention relates to pumps, and moreparticularly to a pump especially adapted for use in an emergencyhydraulic system for aircraft.

It is a well known practice in the aircraft industry today to provide anemergency hydraulic system for operating the control surfaces andauxiLary equipment when the primary system fails. Quite generally thepower source for these systems comprises a motor-pump combination inwhich the motor is a ram-air turbine mounted outsideV the aircraft inthe air stream. The torque developed by such a turbine is proport.onalto its rotational speed, and in order to preclude stalling of theturbine it is advisable to equate the load which the pump imposes on themotor to vthe available torque.

Heretofore, in such systems, constant displacement hyclraulic pumps havebeen used in conjunction with flowsensihve pressure relief valves whichfunction to limit the pressure in the system. These valves'relate themaxi- -mum system pressure to the rate of flow and consequently equatethe load imposed on the turbine by the pump `to the rotational speed ofthe pump and turbine.

' When, in these conventional systems, neither the control surfaces northe auxiliary equipment is being opl erated, the entire delivery fromthe pump is by-passed through the relief valve to the reservar. Thisconstant circulation of hydraulic uid through a iiow restrictor causesanincrease in fluid temperature which adversely affects the performanceof the system and ultimately leads to serious maintenance problems.Furthermore, the back-pressure created by this relief valve imposes acontinuing load on the pump which in turn loads the turbine. Since theturbine is in the air stream, this continuing load producesanunnecessary and undesirable drag on the aircraft.

` The object of this invention is to provide a pump which 'loads itsprime mover in relation to the speed of the latter and which eliminatestheneed for the flow-sensitive relief valve and therefore is free fromthe disadvantages associated therewith.` Basically the inventioncomprises the combination of a variable delivery pump whose displacementis normally governed by discharge pressure, and a device which sensesrate of discharge and modifies the effect of the pressure control inaccordance therewith. In this way the pressure at which pumpdisplacement reduces to a minimum can be made to increase withincreasing displacement'thereby relating the load (which is a functionof pressure) to the speed (which determines rate of flow). Further,since the rate of discharge from the pump itself is now related to theload imposed on the turbine, the need for a flow-sensitive relief valveceases and its inherent disadvanatges are avoided.

A preferred embodiment of the invention will now be described inrelation to the accompanying drawing which is a longitudinal section ofthe combined pump and displacement control mechanism.

Referring to the drawing, the pumpcomprises a housing having twosections 1 and 2 which are joined by suitable bolts 3, and which areformed with mating shoulders ICC for securely clamping and holding acylinder block 4`,

The section 1 is cored, as shown, to provide an inlet chamber 5 whichcommunicates with a supply reservoir via inlet port 6. Bearings 7 and 8are mounted in the left-hand end of this section to receive a shaft 9which is bored and splned at one end to engage a similarly formedcoupling member 11. The opposite end of the shaft is enlarged andshaped, as shown, to form a wobble plate 12. i

The cylinder block 4 is bored at a plurality of circumferentially spacedpoints to provide an annular series of cylinders 13. These cylindersreceive the pistons 14 which reciprocate therein under the action ofwobble plate v12 and nutating plate 15. Each of the cylinders 13communicates w-th the inlet chamber 5 via chamber 16, passage 17,chamber 18 and passage 19. The fluid discharging from these cylindersows through springbiased check valves 21 to annular discharge chamber22'.

A hollow bushing 23 is mounted in the right-hand end of' cylinder block4 for slidably receiving the rod 24. This bushng has a central chamber25 connecting two coaxial bores 26 and 27 of different diameters. 24 isformed with two axially extending portions of different diametersseparated by an annular groove 28; the smaller diameter portion beingslidably received in bore 26 and the larger portion being received inbore 27. The central chamber 25 surrounding the groove 28 communicateswith the annular discharge chamber 22 via radial passage 29, passage 31and choke 32.

Each of thepistons 14 contains a plurality of radia bleed passages 33which cooperate with the spill-back valves 34, slidably surrounding thepistons, for controlling the Veffectye stroke of the pistons. Thesevalves are attached to the rod 24 by the spider 35 which en.- gagesannular grooves formed in the surface of the valves. The valves are'normally held in the position shown in the drawing by spring 36 whichacts on a plate 37, secured to the right-hand end of rod 24, for biasingthe spider into contact with stop 38. As shown, the spring 36 reacts onan ladjustable seat 39.

Up to this point the descnption has related to a wel known variabledisplacement wobble plate pump which `will be readily recognized byanyone skilled in the art. The present invention constitutes animprovement of this basic pump which adapts it for use in the peculiarenvironment previously discussed. The invention comprises the provisionof an enlarged cylinder 41 formed in the housing section 2 which snuglybut slidably receives the p.ston 42 carried by rod 24. This cylinder, in

Operation of the invention In operation, the pump would'be driven by asuit- Y able prime mover, such as a ram-air turbine, through thecoupling member 11, and the inlet and discharge'ports 6 and 47 would .beconnected to the supply and demand portions, respectively, of anhydraullc control system.

As the shaft 9 rotates, the wobble plate 12 and nutating plate 15 willcause the pistons 14 to reciprocate in cylinders 13. This movement ofthe pistons draws uid from the inlet port 6 through chamber 5, passage19, chamber 18' and passage 17 to the chamber 16 and cylinders 13. Fromthe cylinders, the lluid is forced under pressure through the checkvalve 21, chamber 22, passage 46 and discharge port 47 to the controlsystem.

As the pressure develops in chamber 22, it is transmitted to chamber 25via choke V32, and passages 31and Patented May 2, 1961 The rod 29. Thispressure acts on the radial faces of annular groove 28 and because ofthe difference in diameter between these two faces, a -net force willdevelop tending tomove the rod to the right againstthe bias of spring36. When the discharge ,pressure approaches a predetermined maximum, theforce acting on rod 24 will overcome the bias of spring 36, and the rod24, spider 35 andspill-back valves 34 will move to the right. Thismovement of the spill-back valves -permits the Ableed ports 33 to beuncovered for a progressively longer interval during the inward travelof the piston, thereby by-passing increasingly greater quantities offiuid from the cylinders 13. When the spring is fully compressed and thespillback valves are in the extreme right-hand position, the pumpdischarge will be at a minimum. It is obvious that when the dischargepressure decreases below this maximum, the pressure force acting on therod 24 will also decrease and the spill-back valves, under the action ofspring 36, will move to the left thereby increasing the pumpdisplacement.

The present invention modifies the previously described conventionalcontrol in kthe following manner. As the uid which discharges from thechamber 22 passes through the orifice 45, it experiences a drop inpressure proportional to the rate of the fiow. The upstream or higherpressure is transmitted by passage 43 to the righthand side of piston42, and the downstream or lower 'pressure is applied to the left-handside of the pistou via passage 44. Because of this pressure unbalanceacross the piston, a net force is developed which tends to move thepiston and the rod 24 to the left in opposition to the uid force atgroove 28. Since it is desirable to keep the pressure drop acrossorifice 45 as small as possible, it is necessary to make the effectivearea of piston 42 considerably larger than the effective area at groove'28 so that the forces acting on these areas will be of the same orderof magnitude.

If the air turbine driving the pump is operating at :high speed, therate of flow through orifice 45 and consequently the force actingonpiston 42 will also be high. yUnder these conditions, the displacementof the pump will not be reduced until the discharge pressure reaches arelatively high value because the force at groove 28 must overcome alarge pressure force at piston 42 in addition to the force of spring 36'before the rod 24 and 'spill-back valves 34 can move to the right.Thus, when the available torque from the turbine 4is high, so too, is'the load imposed by the pump.

Now if the speed of the turbine is reduced, the fiow `through theorifice and the force acting on piston 42 will decrease. Under theseconditions, the force required at' Agroove 28 to move the rod 24 to theright will be less than before and therefore the maximum dischargepresysure will be lower. Thus, as turbine torque decreases, 'the loadimposed by thepump is correspondingly reduced.

It should now be obvious that the present invention affords a simple andeffective way of relating the load which the pump imposes on the turbineto the available torque output of the turbine. Further, because of thisrelationship, the pump discharges fiuid only as long as Athe dischargepressure is below the maximum established .for any particular pumpspeed. Therefore, since the pump does not supply an excess of hydraulicfluid which must be by-passed during periods of system inactivity, 4therelief valve with its inherent heating and loading disadvantages can beeliminated.

As stated above, the drawing and description relate only to a preferredembodiment of the invention and itwill be readily apparent to oneskilled in the Vart that .there are many 'changes which can be made inthis structure without departing from the inventive concept. The scopeof the invention should not be limited in any respect, except inaccordance ywith the following claims.

What is claimed is:

.1...In.combination, apump-havingadischarge passage;

4 adjustable means movable between minimum and maximum displacementestablishing positions for varying the effective displacement of thepump; biasing means connected with the adjustable means for urging ittoward its maximum displacement establishing position; actuating meansconnected with' the' adjustable means and responsive to the pressure in.the discharge passage of the pump for moving the adjustable meanstoward its minimum displacement establishing position against the biasof the biasing means; and means separate from the actuating means andassociated with the discharge passage and with the biasing means `forprogressively varying the bias exerted by the biasing means directly inaccordance with variations in the rate of discharge from the pump.

2. ln combination, a pump having a discharge passage; adjustable meansmovable between minimum and maximum displacement establishing positionsfor varying the effective displacement of the pump; yielding meansconnected with the adjustable means for biasing it toward its maximumdisplacement establishing position; a metering orifice located in thedischarge passage; and first and second separate pressure responsivemeans in fluid communication with the discharge passage and acting onsaid adjustable means in opposition to each other, the first means beingresponsive to the pressure drop across said metering orifice and actingin aid of said yielding means, and the second means being responsive tothe pressure in the. discharge passage of the pump and operable to movethe adjustable means toward its minimum displacement establishingposition against the bias of the yielding means and the first pressureresponsive means.

3. In combination, a pump having an inlet passage and a dischargepassage; adjustable means movable between minimum and maximumdisplacement establishing positions for varying the effectivedisplacement of the pump; spring means connected with the adjustablemeans for biasing it toward its maximum pump displacement establishingposition; a metering orifice in the discharge passage of the pump; adouble-acting movable abutment operatively connected with the adjustablemeans and in fiuid communication with the discharge passage, one side ofsaid abutment being subject to the pressure upstream of the meteringorifice and operable to urge the adjustable means toward its maximumdisplacement establishing'position, and the other side being subject tothe pressure downstream of said orfiice and operable to urge theadjustable means in the opposite direction; and a second movableabutment in uid communication with the discharge passage and operativelyconnected with the -adjustable means, the effective area of the secondabutment being much smaller than the effective area of the double-actingmovable abutment, the second abutment being subject to the pressure inthe discharge passage of the pump and operable to urge the adjustablemeans toward its minimum displacement establishing position against thebias of the spring means and the double-acting movable abutment.

References Cited in the file of this patent UNITED STATES PATENTS1,052,172 Rateau ...Feb. 4, 19.13 1,280,477 Hopkins Oct. 1, 19181,467,522 Amsler Sept. 11, 1923 1,899,396 Ray Feb. 28, 1933 2,018,119Brouse Oct. 22, 1935 2,102,865 Vickers Dec. 21, 1937 2,411,574 Hunt Nov.26, 1946 2,512,799 .Huber June 27, 1950 2,562,615 Huber July 31, 19512,600,632 French June 17, 1952 2,600,633 French June 17, 1952 ,2,678,533Lawrence May 18, 1954 2,747,598 Wooldridge May 2 9, 195,6 '2,944,488Meyer July 12, 1960

